The effects of the government shutdown in Washington could also be felt on Sunday, as staff furloughs in key government departments made it difficult for journalists to obtain information.

The seizure in Tripoli of the alleged al-Qaida operative Abu Anas al-Liby prompted the Libyan government to issue an angry statement, questioning the US account that Liby had been detained with its full knowledge. The statement said: "As soon as it heard the reports, the Libyan government contacted the United States authorities to demand an explanation [for] the kidnapping of a Libyan citizen."

George Little, the Pentagon press secretary, said on Sunday that Liby had been designated a "specially designated global terrorist" under executive order 13224 – an order issued by president George W Bush two weeks after the 9/11 attacks. Liby is also listed as a subject of the US rewards for justice programme, Little said, and is listed on the UN's al-Qaida sanctions list.

Liby was being "detained lawfully by the Department of Defense", a defence official told the Guardian on Sunday afternoon. The Libyan was indicted in New York in 2000, for his alleged role in bombings on US embassies in Kenya and Tanzania two years earlier.

The Department of Defence refused to give further information about Saturday's operation in Somalia, which it said was "aimed at capturing an al-Shabaab terrorist leader". US special forces approached a compound in Barawe and were engaged in a gun battle before pulling out.

A spokesman for the Department of Defense would not comment when asked why the operation used ground forces instead of drone strikes. The spokesman did not elaborate on why US special forces had been forced to withdraw before capturing the target.

The defence secretary, Chuck Hagel, on Sunday issued a statement that praised the raids in Libya and Somalia and said they showed America would "spare no effort to hold terrorists accountable".

"I want to commend all of the service members who were involved in the planning and execution of these two operations, which demonstrate the unparalleled precision, global reach, and capabilities of the United States military," Hagel said.

The Department of Justice will determine where Liby will be tried – at Guantánamo Bay or in a federal court – but reporters calling the department's press office on Sunday were met with an answer-phone message. The message said: "In the event of a lapse in appropriations this message will be listened to and responded to upon a funding resolution."

Attempts to contact the White House press office met a similar response. An answer-phone message said: "This office remains open during the lapse in appropriations but with greatly reduced staffing. We are available to handle urgent or emergency requests but no one is available at this time to take your call."

The message suggested sending an email, which had not been replied to at the time of publication.